1. Field of Invention
The present invention relates to a one-way wrench.
2. Related Prior Art
Taiwan Patent Publication No. 281946 teaches a one-way wrench including a head 10, an annular gear 20, an engagement block 13 and a spring 14. The head 10 defines a circular space 11 and a crescent space 111 communicated with the circular space 11. A wall of the crescent space 111 defines a recess 112. The annular gear 20 includes an external face formed with a plurality of teeth 23 and an internal face 24 for engagement wit a nut or a head of a bolt. The engagement block 13 includes a convex face formed with a boss 131 and a concave face formed with a plurality of teeth 132. The spring 14 includes an end receiving the boss 131. The engagement block 13 and the spring 14 are received in the crescent space 111. Normally, the teeth 132 are engaged with some of the teeth 23. The convex face contacts the wall of the crescent space 111. As the head 10 is rotated in a first direction, the annular gear 20 engaged with the nut or the head of the bolt tends to rotate the engagement block 13 in a second direction opposite to the first direction relative to the head 10, thus enhancing the contact of the convex face with the wall of the crescent space 111 and the engagement of the teeth 132 with the teeth 23. Thus, rotation in the first direction of the head 10 relative to the annular gear 20 is avoided. Therefore, the head 10 rotates the annular gear 20 in the first direction together with the nut or the head of the bolt clockwise. When the head 10 is rotated in the second direction, the annular gear 20 engaged with the nut or the head of the bolt is allowed to rotate the engagement block 13 in the first direction relative to the head 10 because the convex face is not hindered by means of the wall of the crescent space 111. Thus, the teeth 132 can be disengaged from the teeth 23 in order to allow rotation of the head 10 relative to the annular gear 20. Therefore, rotation of the head 10 in the second direction does not cause rotation of the annular gear 20 in the second direction together with the nut or the head of the bolt.
Taiwan Patent Publication No. 335750 teaches a one-way wrench including a head, an annular gear 35, an engagement block 40, a base 50 and a spring 60. The head defines a crescent space 31 and a circular space 32 and communicated with the crescent space 31. A wall of the crescent space 31 defines a recess 34. The annular gear 35 includes an internal face for engagement with a nut or a head of a bolt and an external face formed with a plurality of teeth 52. The engagement block 40 includes a plurality of teeth and a convex face and defines a recess. The base 50 defines a channel and includes a convex face and a boss 51 formed on the convex face. The spring 60 includes an end received in the recess defined in the engagement block 40 and an opposite end inserted in the channel defined in the base 50. The engagement block 40, the base 50 and the spring 60 are received in the crescent space 31. The boss 51 is received in the recess 34. The annular gear 35 is received in the circular space 32. Normally, the teeth of the engagement block 40 are engaged with some of the teeth of the annular gear 35. The convex faces contact the wall of the crescent space 31. As the head is rotated in a first direction, the annular gear 35 engaged with the nut or the head of the bolt tends to rotate the engagement block 40 in a second direction opposite to the first direction relative to the head, thus enhancing the contact of the convex face of the engagement block 40 with the wall of the crescent space 31 and the engagement of the teeth of the engagement block 40 with the teeth of the annular gear 35. Thus, rotation in the first direction of the head relative to the annular gear 35 is avoided. Therefore, the head rotates the annular gear 35 in the first direction together with the nut or the head of the bolt. When the head is rotated in the second direction, the annular gear 35 engaged with the nut or the head of the bolt is allowed to rotate the engagement block 40 in the first direction relative to the head because the convex face of the engagement block 40 is not hindered by means of the wall of the crescent space 31. Thus, the teeth of the engagement block 40 can be disengaged from the teeth of the annular gear 35 so as to allow rotation of the bead relative to the annular gear 35. Therefore, rotation of the head in the second direction does not cause rotation of the annular gear 35 in the second direction together with the nut or the head of the bolt. Fabrication and mounting the base 50 require effort and therefore increase its cost.
Taiwan Patent Publication No. 431260 teaches a one-way wrench including a head 20, an annular gear 50, an engagement block 30, a seesaw 40 and a spring 44. The head 20 defines a circular space 22 and a crescent space 23 communicated with the circular space 22. The annular gear 50 includes an internal face for engagement with a nut or a head of a bolt and an external face formed with a plurality of teeth 52. The engagement block 30 includes a plurality of teeth 32 and a convex face 34 and defines a recess 35. The seesaw 40 includes a convex face 41, two corners 42 and an end 43. The spring 44 includes an end fit in the recess 35 and an opposite end in which the end 43 of the seesaw 40 is fit. The engagement block 30, the seesaw 40 and the spring 44 are movably received in the crescent space 23. The annular gear 50 is received in the circular space 22. When the head 20 is rotated in a first direction, the annular gear 50 contacts one of the corners 42, thus pivoting the engagement block 30 to the annular gear 50. Thus, the teeth 32 are engaged with some of the teeth 52 so that the annular gear 50 engaged with the nut or the head of the bolt tends to rotate the engagement block 30 in a second direction opposite to the first direction relative to the head 10, thus enhancing the contact of the convex face 34 with the wall 24 and the engagement of the teeth 32 with the teeth 52. Therefore, rotation in the first direction of the head 20 relative to the annular gear 50 is avoided. The head 20 rotates the annular gear 50 in the first direction together with the nut or the head of the bolt. When the head 20 is rotated in the second direction, the annular gear 50 contacts both the corners 42 so as to pivot the engagement block 30 from the annular gear 50. Thus, the teeth 32 are disengaged from the teeth 52 so as to allow rotation of the head 20 relative to the annular gear 50. Therefore, rotation of the head 20 in the second direction does not cause rotation of the annular gear 50 in the second direction together with the nut or the head of the bolt. The engagement block 30 may not be engaged with or disengaged from the annular gear 50 as desired since the engagement block 30, the seesaw 40 and the spring 44 can slide together in the crescent space 23. Moreover, fabrication and installment of the seesaw 40 requires effort and therefore increase its cost.
The present invention is therefore intended to obviate or at least alleviate the problems encountered in prior art.
It is the primary objective of the present invention to provide a one-way wrench that is simple in structure and low in cost.
According to the present invention, a one-way wrench includes a head, a gear, an engagement element and a bent spring. The head defines a circular space and a crescent space communicated with the circular space. The gear includes a plurality of teeth, and is received in the circular space. The engagement element includes a concave face formed with a plurality of teeth and a convex face, and is received in the crescent space. The teeth of the engagement element are engaged with some of the teeth of the gear. The convex face contacts a wall of the crescent space. The bent spring includes first and second sections, and is received in the crescent space so that the first section of the spring contacts the wall of the crescent space and the second section of the spring contacts the engagement element. When the head is rotated in a first direction, the gear tends to rotate the engagement element relative to the head in a second direction opposite to the first direction so as to enhance the engagement of the teeth so as to avoid rotation of the head relative to the gear. When the head is rotated in the second direction, the gear rotates the engagement element in the first direction relative to the head since the convex face is not hindered via the wall of the crescent space, thus disengaging the teeth of the engagement element from the teeth of the gear so as to allow rotation of the head relative to the gear.
Other objectives and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the attached drawings.